Burner assembly for a combustor of a gas turbine power plant and combustor comprising said burner assembly

ABSTRACT

A burner assembly for a combustor is provided with a pilot burner extending along a longitudinal axis and a premix burner surrounding the pilot burner; the pilot burner being integral with the premix burner.

PRIORITY CLAIM

This application claims priority from European Patent Application No.17155917.2 filed on Feb. 13, 2017, the disclosure of which isincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a burner assembly for a combustor of agas turbine power plant.

Moreover, the present application refers to a combustor comprising saidburner assembly.

DESCRIPTION OF PRIOR ART

As known, a gas turbine power plant (in the following only gas turbineplant) comprises a rotor provided with an air compressor, with at leastone combustor, which is arranged downstream of the compressor and fedwith the air coming from the compressor, and with at least one gasturbine, which is arranged downstream of the combustor and fed with thegas coming from the combustor that has undergone combustion.

More in detail, the compressor comprises an inlet supplied with air anda plurality of blades and vanes configured for compressing the airentering the compressor. The compressed air leaving the compressor flowsinto a plenum and from there into at least one burner assembly of thecombustor. Inside the burner assembly, the compressed air is mixed withat least one fuel. The mixture of such fuel and the compressed air isthen combusted. The resulting hot gas leaves the combustor chamber andexpands in the turbine performing work on the rotor.

The burner assembly used in gas turbine plants of the last generationare preferably of the premix type, as they are characterized by lowemissions. This kind of burner assembly is known, for example fromdocument US 2007/0231762. Said burner assembly comprises a premix burnerand a pilot burner. The premix burner is configured so as to swirlincoming combustion air and mix it with the fuel into a premix region.

The pilot burner comprises a pilot lance centrally arranged in theburner assembly. At low operating loads, the pilot lance is configuredto inject fuel into the combustion air axially in order to createfuel-rich zones ensuring that flame being not extinguished. At higheroperating loads, the injection of fuel via the pilot lance is lowered inorder to reduce pollutants, and the injection of fuel via the premixburner is increased.

The burner assemblies of this known type have a structure made of aplurality of component parts that need to be assembled together.Therefore the assembling of each burner assembly require several stepsand is, consequently, highly burdensome.

An object of the present invention is therefore to provide a burnerassembly for a combustor that enables avoiding, or at least mitigating,the described drawbacks.

In particular, it is an object of the present invention to provide aburner assembly which has a simplified structure in order to reduce theassembling costs and, at the same time, is sufficiently reliable.

According to the present invention, there is provided a burner assemblyfor a combustor comprising a pilot burner extending along a longitudinalaxis; a premix burner surrounding the pilot burner; the pilot burnerbeing integral with the premix burner.

In this way the structure of the burner assembly is noticeablysimplified. The number of the component parts of the burner assembly isin fact reduced and the pilot burner has a reduced axial length withrespect to the prior art solutions as the burner assembly can be fixedonly to the combustor wall and the pilot burner and the premix burner donot need any more to be coupled to other fixed structures of thecombustor (i.e. pressure vessel) or of the gas turbine plant as normallymade in prior art solution. Thanks to the reduced axial length of thepilot burner, the thermal expansion displacement of the pilot burner areadvantageously reduced. Moreover, the fact that the burner assembly canbe fixed only to the combustor wall greatly simplifies the assemblyoperation with evident advantages in terms of saving costs and time.

According to a preferred embodiment of the present invention, the premixburner and the pilot burner are a monolithic body.

In this way also the assembling time and costs are noticeably reduced.

According to a preferred embodiment of the present invention, the premixburner and the pilot burner are two separated pieces fixed together.

According to a preferred embodiment of the present invention, the pilotburner is fixed to an inner surface of the premix burner.

According to a preferred embodiment of the present invention, the premixburner comprises an inlet portion coupled to a fuel supply assembly andan injection portion extending, in use, about the longitudinal axis andcoupled to the inlet portion.

According to a preferred embodiment of the present invention, theinjection portion is provided with a first end and a second end; thesecond end having a second section diameter lower than a first sectiondiameter of the first end; the inlet portion being coupled to the secondend.

According to a preferred embodiment of the present invention, the pilotburner is fixed to the inlet portion of the premix burner.

According to a preferred embodiment of the present invention, the pilotburner is fixed to the inlet portion of the premix burner along at leasttwo contact zones axially displaced. In this way the fixing between thepilot burner and the premix burner is furthermore stable and reliable.

According to a preferred embodiment of the present invention, the pilotburner and the premix burner are fixed together so as to define asliding interface between the pilot burner and the premix burner. Inthis way relative axial displacements due to thermal expansions betweenthe pilot burner and the premix burner are allowed.

According to a preferred embodiment of the present invention, thesliding interface is defined by an air gap between the pilot burner andthe inlet portion of the premix burner.

According to a preferred embodiment of the present invention, the pilotburner comprises at least two concentric conduits; at least one of theconduits being provided with an extendible portion.

In this way relative axial displacements in the pilot burner due tothermal expansions are compensated.

According to a preferred embodiment of the present invention, the premixburner comprises at least one fuel supply conduit provided with afurther extendible portion. In this way relative axial displacements inthe premix burner due to thermal expansions are compensated.

A further object of the present invention is to provide a combustor fora gas turbine power plant having a simplified structure.

According to the present invention, there is provided a combustor for agas turbine according to claim 12.

The present invention will now be described with reference to theaccompanying drawings, which illustrate some non-limitative embodiment,in which:

FIG. 1 is a schematic section view, with parts removed for sake ofclarity, of the burner assembly according to the present invention;

FIG. 2 is a schematic section view, with parts removed for sake ofclarity, of the burner assembly according to a second embodiment of thepresent invention.

Reference number 1 in FIG. 1 indicate a burner assembly for a combustor9 of a gas turbine power plant (here only partially illustrated).

Burner assembly 1 comprises a pilot burner 2 extending along alongitudinal axis A and a premix burner 3 extending about the pilotburner 2.

Pilot burner 2 and premix burner 3 are coupled to a fuel supply assembly4 (schematically represented in the attached figures) which is connectedto a respective fuel supply circuit (not illustrated). In thenon-limiting here disclosed and illustrated, the fuel supply assembly 4is arranged along the longitudinal axis A. However, variants of the fuelsupply assembly 4 can be provided in order to supply the fuel from othersides of the burner assembly 1. For example, fuel supply assembly 4 cancomprise metal rigid hoses or/and flexible hoses connected to the pilotburner 2 and to the premix burner 3.

The pilot burner 2 comprises a lance 5 which is provided with a firstconduit 6 supplied, in use, with a first fuel, with a second conduit 7supplied, in use, with air and with a third conduit 8 supplied, in use,with a second fuel.

Preferably the first fuel is gas and the second fuel is fuel oil.

Preferably the first conduit 6, the second conduit 7 and the thirdconduit 8 are concentric and extends about the longitudinal axis A.

In the non-limiting example here disclosed, the third conduit 8 extendsalong the longitudinal axis A, the first conduit 6 extends about thethird conduit 8 and the second conduit 7 extends about the first conduit6.

The first conduit 6 and the third conduit 8 are supplied with therespective first fuel and second fuel by the fuel supply assembly 4. Inparticular the fuel is supplied along a flow direction D (indicated byan arrow in FIGS. 1 and 2) towards the inside of the combustor 9.

The second conduit 7 has an axial length lower than the axial length ofthe first conduit 6 and the third conduit 8.

The lance 5 has an end tip 10 which faces inside the combustor 9.

The lance 5 is schematically represented in the attached drawings.Preferably the lance 5 is provided with a plurality of first nozzles(not illustrated) connected to the first conduit 6, with a plurality ofsecond nozzles (not illustrated) connected to the second conduit 7 andwith a plurality of third nozzles (not illustrated) connected to thethird conduit 8.

The lance end tip 10 has preferably a circular section and is providedwith a circular edge 15. The end tip 10 comprises an end surface 16which is defined by a respective end wall 17 and is preferably planar.

The premix burner 3 extends about the pilot burner 2 and substantiallycomprises an inlet portion 20 coupled to the supply assembly 4, aninjection portion 21 coupled to the inlet portion 20 and an outletportion 22 coupled to the injection portion 21 and to the combustor 9.

The inlet portion 20 comprises a fuel supply conduit 23 which ispreferably annular and extends about a respective inlet portion of thepilot burner 2.

The dimensions of the fuel supply conduit 23 are designed so as to allowan easy insertion of the pilot burner 2 into the substantiallycylindrical seat defined by the fuel supply conduit 23.

The fuel supply conduit 23 is supplied with fuel by the fuel supplyassembly 4 along a flow direction D (indicated by an arrow in FIGS. 1and 2) towards the inside of the combustor 9. The fuel supplied to thefuel supply conduit 23 is gas.

In the fuel supply conduit 23 are arranged a plurality of air inletchannels 24 (represented in dotted lines) which are configured to supplyair to the second conduit 7 of the pilot burner 2. The air suppliedthrough the air inlet channels 24 is air collected in a plenum 25 (onlypartially visible in the drawings) in communication with the outlet ofthe compressor of the plant.

The injection portion 21 is preferably defined by a truncated-coneshaped swirler 26 provided with air slots 27 (the air slots are not wellvisible in the attached drawings—dotted arrows indicate the air flowingthrough said air slots) and fuel nozzles 28.

The air slots 27 are supplied with the air collected in the plenum 25 incommunication with the outlet of the compressor of the plant.

Fuel nozzles 28 are supplied with fuel by the fuel supply conduit 23.

The injection portion 21 is provided with a first end 29 a and a secondend 29 b; the second end 29 b having a section diameter lower than thesection diameter of the first end 29 a.

The inlet portion 20 is coupled to the second end 29 b, while the outletportion 22 is coupled to the first end 29 a.

Preferably, the injection portion 21 is made by two shells assembledtogether.

The outlet portion 22 has preferably a cylindrical shape and isgenerally defined as CBO (cylindrical burner outlet). The outlet portion22 is coupled to a wall 31 of the combustor 9.

The pilot burner 2 and the premix burner 3 are integral.

In other words, the pilot burner 2 and the premix burner 3 are rigidlyfixed together.

Preferably, the pilot burner 2 is fixed to at least a portion of aninner surface of the premix burner 3. The inner surface of the premixburner 3 is the surface of the premix burner 3 facing, in use, the pilotburner 2.

In the non-limiting example here disclosed and illustrated, the premixburner 3 and the pilot burner 2 are two separated pieces fixed together.Preferably, the premix burner 3 and the pilot burner 2 are directlyfixed together.

According to an embodiment not illustrated, the premix burner 3 and thepilot burner 2 can be made as a monolithic body. For example, themonolithic body can be obtained by additive manufacturing or by castingprocesses.

In detail, the pilot burner 2 is fixed to the inlet portion 20 of thepremix burner 3. In particular, the outer surface of the pilot burner 2is fixed to the inner surface of the inlet portion 20 of the premixburner 3.

In the non-limiting example illustrated in FIG. 1, the outer surface ofthe second conduit 7 is fixed to the inner surface of the inlet portion20.

Preferably, the outer surface of the second conduit 7 is fixed to theinner surface of the inlet portion 20 at the boundary with the injectionportion 21.

Preferably, the fixing of the pilot burner 2 is made along at least onecontact zone 30 (schematically represented in the attached figure by ablack dot) of the inner surface of the inlet portion 20.

The fixing of the pilot burner 2 to the inner surface of the inletportion 20 can be made, for example, by welding, by bolts or by clampingmeans, by casting of by additive manufacturing.

According to a variant illustrated in FIG. 2, the pilot burner 2 and thepremix burner 3 are fixed together so as to define a sliding interface35 between the pilot burner 2 and the inlet portion 20 of the premixburner 3.

Said sliding interface 35 allows relative axial movements between thepilot burner 2 and the premix burner 3 due to thermal expansions.

In the non-limiting example here disclosed and illustrated, the slidinginterface 35 is defined by an air gap 36 between the pilot burner 2 andthe inlet portion 20 of the premix burner 3.

Preferably, the sliding interface 35 is defined by an air gap 36 betweenthe outer surface of the second conduit 7 and the inner surface of theinlet portion 20 of the premix burner 3.

The air gap 36 is preferably arranged along the inlet portion 20 nearthe injection portion 21.

The outer surface of the pilot burner 2 is fixed to the inner surface ofthe inlet portion 20 of the premix burner 3.

In the non-limiting example illustrated in FIG. 2, the outer surface ofthe first conduit 6 is fixed to the inner surface of the inlet portion20.

Preferably, the inner surface of the inlet portion 20 is fixed to theouter surface of the first conduit 6 near the beginning of the secondconduit 7.

Analogously to the embodiment of FIG. 1, the fixing of the pilot burner2 is made along at least one contact zone 30 (schematically representedin the attached figure by a black dot) of the inner surface of the inletportion 20.

The fixing of the pilot burner 2 to the inner surface of the inletportion 20 can be made, for example, by welding, by bolts or by clampingmeans, by casting of by additive manufacturing.

According to one variant not illustrated, the fixing of the pilot burner2 to the premix burner 3 can be made along at least two contact zonesaxially displaced in order to ensure a more stable coupling. Forexample, the pilot burner 2 and the premix burner 3 can be coupledaccording to a combination of the coupling illustrated in FIG. 1 andFIG. 2.

With reference to both the embodiments of FIG. 1 and FIG. 2 the firstconduit 6, the second conduit 7 and the third conduit 8 of the pilotburner 2 and the fuel supply conduit 23 of the premix burner 3 areprovided with at least one extendible portion 37.

These extendible portions 37 can be provided in order to compensate theaxial displacement due to thermal expansions of the first conduit 6, thesecond conduit 7 and the third conduit 8 of the pilot burner 2 and ofthe fuel supply conduit 23 of the premix burner 3.

In the embodiment shown in FIG. 2, wherein a sliding interface 35 isprovided between the pilot burner 2 and the inlet portion 20 of thepremix burner 3, the second conduit 7 does not require the extendibleportion as the thermal expansions are compensated by the sliding betweenthe pilot burner 2 and the inlet portion 20 of the premix burner 3.

In the non-limiting example here disclosed and illustrated, theextendible portions 37 are defined by a corrugated portions of theconduit.

According to a variant not illustrated, the extendible portions can bedefined by a helical wrapped portion of the conduit.

Finally, it is clear that modifications and variants can be made to theburner assembly and to the combustor described herein without departingfrom the scope of the present invention, as defined in the appendedclaims.

1. Burner assembly for a combustor, the burner comprising: a pilotburner extending along a longitudinal axis (A); and a premix burnersurrounding the pilot burner; the pilot burner being integral with thepremix burner.
 2. Burner assembly according to claim 1, wherein thepremix burner and the pilot burner are a monolithic body.
 3. Burnerassembly according to claim 1, wherein the premix burner and the pilotburner are two separated pieces fixed together.
 4. Burner assemblyaccording to claim 1, wherein the pilot burner is fixed to an innersurface of the premix burner.
 5. Burner assembly according to claim 3,wherein the premix burner comprises: an inlet portion coupled to a fuelsupply assembly; and an injection portion extending, when in use, aboutthe longitudinal axis (A) and coupled to the inlet portion.
 6. Burnerassembly according to claim 5, wherein the injection portion is providedwith a first end and a second end, the second end having a secondsection diameter lower than a first section diameter of the first endand the inlet portion being coupled to the second end.
 7. Burnerassembly according to claim 5, wherein the pilot burner is fixed to theinlet portion of the premix burner.
 8. Burner assembly according toclaim 7, wherein the pilot burner is fixed to the inlet portion of thepremix burner along at least two contact zones axially displaced. 9.Burner assembly according to claim 4, wherein the pilot burner and thepremix burner are fixed together so as to define a sliding interfacebetween the pilot burner and the premix burner.
 10. Burner assemblyaccording to claim 9, wherein the sliding interface is defined by an airgap between the pilot burner and an inlet portion of the premix burner.11. Burner assembly according to claim 1, wherein the pilot burnercomprises: at least two concentric conduits, at least one of the twoconcentric conduits being provided with an extendible portion. 12.Burner assembly according to claim 1, wherein the premix burnercomprises: at least one fuel supply conduit provided with a furtherextendible portion.
 13. Combustor for a gas turbine power plant thecombustor comprising: the burner assembly claimed in claim 1.